On top of that, Tesla is racing to boost production at new plants in Texas and Berlin amid supply-chain snarls and higher raw materials costs, as well as get work at its biggest factory in Shanghai back on track during a spike in COVID-19 cases there. Musk said in January Tesla had too much on its plate and would not introduce new models like Cybertruck this year.
Tesla has managed to outrace its problems, but a heavier pull of his focus by Twitter worries investors.
"I fear this is going to be a distraction," said one fund manager with a significant position in Tesla who asked not to be identified. "He's juggling supply chains and factory delays and the expansion of the energy storage business and this doesn't fit at all."
Shares of Tesla have slid 8 percent since Musk first disclosed his initial stake in Twitter.
Tesla could not be reached for comment, but one insider at the company who asked not to be identified said investor concerns were "overdone" and Musk was still heavily engaged at the automaker.
Musk also leads rocket company SpaceX, as well as brain-chip startup Neuralink and tunneling venture the Boring Company.
Tesla has seen executive turnover before with the departure of co-founder JB Straubel in 2019 and president Jerome Guillen last year.
Tesla, founded in 2003, has grown into the most valuable automaker but there are only two executives listed along with Musk in its leadership team on the company website, compared with 17 at General Motors and 11 at Volkswagen Group.
Tesla's current high-profile leadership outside of Musk includes CFO Zachary Kirkhorn and Senior Vice President Andrew Baglino, who handles the powertrain development. Both are known to investors from their appearances on Tesla's quarterly earnings conference calls.
Robert Pavlik, senior portfolio manager at Dakota Wealth in Fairfield, Conn., that owns a limited number of Tesla shares in accounts he manages, wondered whether Musk would simply install someone else to lead Twitter.
"It seems like that would be the most logical thing," he said. "It seems like he has his hands full with Tesla and SpaceX."
Gerber said perhaps Musk needs a strong No. 2 executive like he has at SpaceX with President Gwynne Shotwell.
Ian Beavis, chief strategy officer at auto consultancy AMCI, worries Musk's purchase of Twitter, with its controversies around political and social issues, could even damage the Tesla brand.
Some investors remain concerned about plans by Musk, who is worth $268 billion according to Forbes, to finance the Twitter deal. Twitter said Musk secured $25.5 billion of debt and margin loan financing and is providing a $21 billion equity commitment. It is unclear whether Musk will sell Tesla shares to help fund the deal.
Musk holds 172.6 million shares in Tesla and he has already borrowed against about half of his stock, according to Tesla filings. If he puts up more shares as collateral to secure margin loans of $12.5 billion he may be left with roughly 30 million unpledged shares, according to a Reuters calculation.